The present disclosure relates to a solid-bowl centrifuge that includes a solid-bowl centrifuge, particularly a solid-bowl screw-type centrifuge, having a centrifugal drum rotatable about a horizontal axis of rotation, which has a weir for draining a liquid out of the centrifugal drum and which weir has a passage with at least one or more passage openings in an axial end region or drum lid characterized.
A solid-bowl centrifuge of the above-mentioned type is known from European Patent Document EP 0 702 599 B1 and U.S. Patent Document U.S. Pat. No. 5,593,377 respectively. These two documents disclose a solid-bowl screw-type centrifuge with a drum, having a weir which is provided with a passage for draining a liquid phase separated in the centrifugal drum, a throttle disk being assigned to the passage. The orifice plate is constructed as a non-rotating part whose distance to the passage is variable, so that an adjustment of the liquid level in the centrifugal drum becomes possible by an axial adjustment of the orifice plate.
The stationary orifice plate has no disadvantageous effect on the method of operation of the centrifugal drum. In particular, there is no disadvantageous braking effect as a result of the liquid passing through an annular gap between the rotating weir and the stationary liquid plate.
The annular gap generates a flow resistance which is greater the shorter the axial distance between the weir and the orifice plate. However, as the flow resistance increases, a greater fluid pressure is required at the passage, which leads to a rise of the liquid level in the centrifugal drum. When the axial distance between the weir and the orifice plate is enlarged, the liquid level in the centrifugal drum will fall to a value caused by the passage of the weir without such an orifice plate.
This solution has been very successful in practice because it can be implemented in a simple and cost-effective manner by a construction of the orifice plate which is stationary during an operation and does not rotate along with the drum. This is, without the necessity of transmitting adjusting forces to co-rotating parts of the centrifuge, and thereby makes it possible to excellently control and/or regulate the separation or clarification operation in the drum.
From International Patent Document WO 01/85349 A1, it is known to implement the axial adjustability of an orifice plate, which does not rotate along and whose method of operation corresponds to that of European Patent Document EP 0 702 599 B. The implementation is between the passage openings of the drum and the orifice plate in that the orifice plate can be swiveled in a flap-type manner about a pivot bearing at its outer circumference by an actuator. By a ring groove, which is called a “ring cup”, the flow conditions at the passage are to be optimized. FIG. 1 herein suggests an embodiment in which a type of cylindrical ring having a wall, which is oriented parallel to the axis of rotation of the drum, is arranged in an annular gap between a stationary housing wall and the centrifuge lid, as well as adjustable apertures through which the drained liquid sprays directly radially to the outside, being arranged in this ring.
German Patent Document DE PS 966 080 shows a solid-bowl screw-type centrifuge whose liquid discharge from the drum is oriented radially to the outside, where the liquid is collected in a type of annulus having an almost circular cross-section. German Patent Document DE PS 706 968 also shows liquid discharges directed radially to the outside from the drum.
German Patent Document DE 25 15 452 also shows a plate behind the axially oriented liquid discharges, which plate rotates along with the drum and deflects the discharging liquid virtually by 180° into the opposite axial direction.
U.S. Pat. Document U.S. Pat. No. 2,083,899 shows a centrifuge with a vertical axis of rotation without an orifice plate.
French Patent Documents FR 20 57 600 and FR 20 54 722 each show solid-bowl screw-type centrifuges with a fluid discharge directed axially with respect to the axis of rotation, where emerging liquid can spray from a wall behind the outlets back again to the drum.
In contrast to the state of the art, as it is known from European Patent Document EP 0 702 599 B1, the present disclosure relates to a more careful discharge of the liquid phase from the weir in a simple manner.
Thus, the present disclosure relates to a solid-bowl centrifuge comprising a centrifugal drum rotatable about a horizontal axis of rotation. The centrifugal drum includes a weir to drain a liquid out of the centrifugal drum. The weir includes a passage having at least one passage opening in an axial end region of the centrifugal drum that includes a drum lid. A deflector plate is arranged outside the centrifugal drum and in front of the drum lid. The deflector plate is stationary during an operation of the centrifugal drum and widens at least in sections as the deflector plate extends away from the centrifugal drum. The deflector plate includes an interior jacket, and a distance of the interior jacket from the horizontal axis of rotation is not constant but widens.
Accordingly, a deflector plate, which is stationary during the operation, that is, does not rotate along with the drum, is arranged in front of the drum lid outside the centrifugal drum and inside a collecting chamber. The deflector plate extends away from the drum lid, widens at least in sections and has at least one interior jacket. A distance of the interior jacket from the axis of rotation is not being constant, but is widening or enlarging.
“Widening” means that the deflector plate is no plane plate but a “sleeve-type” component with an inside diameter which changes, for example, enlarges, at least over a portion of the axial dimension or the entire axial dimension. The deflector plate therefore has a defined axial dimension, as an extension of the axis of rotation of the drum, as well as an interior and exterior jacket. A distance of the interior jacket from the axis of rotation not being constant but being widened or enlarged.
The widening deflector plate has an opening angle γ with respect to a plane extending perpendicularly to the axis of rotation D of the drum or parallel to the drum lid. Opening angle γ is greater than 0° and smaller than 90°. The widening deflector plate at the interior jacket therefore has an angle of 90°−γ with respect to the axis of rotation (D) of the drum, which is greater than 0° and smaller than 90°.
The deflector plate has such a shape or is arranged or integrated in the arrangement such that the liquid first exits axially to the outside from the drum until it impacts on a wall or plate. From that impact, the liquid sprays essentially radially to the outside, the liquid arriving on the widening deflector plate which prevents the exiting liquid from directly radially impacting on a wall or walls, such as walls oriented parallel to the axis of rotation, of the collecting chamber. Thus, the development of noise is reduced in comparison to an arrangement without the deflector plate.
The liquid first exits axially, that is, parallel to the axis of rotation of the drum, from the drum to the outside until it impacts on a wall by which it is directed essentially radially to the outside. Here, it impacts on the widening deflector plate which prevents the exiting liquid from arriving at the drum again.
The widening geometry of the deflector plate has several advantages. For example, it permits a clear reduction of the operating noise of the centrifuge because the liquid sprays no longer directly from the annular gap between the orifice plate or another component and the drum lid against walls of the collecting chamber but is deflected by an angle which corresponds to the opening angle of the deflector plate. As a result, the liquid no longer arrives perpendicularly on the housing walls of the collecting chamber which clearly reduces the development of noise. In view of the high number of revolutions of, for example, 3,500 r.p.m., this is a significant advantage in practice.
In addition, because of the “softer” impacting of a liquid jet on the walls of the collecting chamber, the foam formation is reduced in the case of products with a tendency to foam.
Another advantage, for example, is a reduction of the power consumption by the initially fast drainage from the interior area, particularly away from the centrifugal drum surface.
An annular gap is formed between the passage and an orifice plate outside the centrifugal drum or between the passage and another component. The annular gap guides the liquid radially to the outside and the annular gap is completely or partially surrounded by the widening deflector plate over its axial dimension, so that the direct radial spraying of the liquid phase out of this annular gap is prevented. The deflector plate has an advantageous effect because it prevents the exiting liquid from impacting again on the drum.
The inside diameter of the deflector plate, for example, is larger than the outside diameter on which the passage openings of the centrifugal drum are arranged.
The deflector plate axially, for example, directly adjoins the passage openings, so that a flowing-out of liquid between the drum lid and the deflector plate is prevented. In another embodiment, projections, such as sleeves, which axially overlap the deflector plate, are provided at the passage openings.
The deflector plate has a ring-type, conically widening shape.
The opening angle of the interior jacket of the deflector plate, for example, amounts to between 5 and 45°, or between 10 and 30°. A clear minimizing of noise can be achieved by using one of the opening angle ranges just mentioned.
The opening angle of the deflector plate may be constant or may change over its axial dimension and/or in the circumferential direction.
A multipart, such as a two-part construction of the deflector plate is conceivable in order to implement its widening shape in a simple manner.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.